Method of treating magnesium and product obtained thereby



Patented Nov. 22,1932

UNITED STATES PATENT ol-"rlcs JOHN A. GANN ANI) WILLIAM H. GROSS, OF MIDLAND, MICHIGAN, ASSIGNOBS TO THE DOW CHEMICAL COMPANY, OF MIDLAND, MICHIGAN, A- CORPORATION OF MICHIGAN I METHOD or TREATING menssium AND rnonoc'r on'ramn'n runner"! No Drawing.

insufiicient etching properties, to which is added another material, in relatively small amount, having etching properties.

It has heretofore been proposed to treat a magnesium article with an emulsion of soap,

oil, and water (United States Patent 1,477;

922) to form a substantially colorless aliphatic soap base coating thereon. which can be dyed if desired. It has also been proposed (United States Patent 1,480,869) to color magnesium and magnesium base alloy articles with a nitric acid solution containing either chromic acid or sodium bichromate and a salt of a heavy metal. We have now found that chromic acid, bichromates and other heavy metal compounds are unnecessary additions to a solution used for coloring magnesium articles. We have also found that it is unnecessary to form a soap base coating on the article before it can be colored. We have further found that materials of an organic aromatic nature can be used in an etching solution for coloring magnesium articles in a much more.

satisfactory manner than heavy metal compounds due partially to the fact that treatment with an etching solution of them suffices for the complete coloring treatment and a much greater range of colors canbe obing and etching bath containing an organic I aromatic coloring agent for magnesium.

Further objects and advantages will appear as the description proceeds. 1

To the accomplishment of the foregoing and related ends, the invention, then, consists of the steps hereinafter fully described and particularly pointed out in theclaims, the following descri tion setting forth in detail several modes 0 carrying out the inven- Application filed May 8, 1931.

Serial No. 536,084.

tion, such disclosed modes illustrating, however, but several of various ways in which the principle of the invention may be used.

Our tests show that colored magnesium and magnesium alloy articles can'be readil produced by subjecting the article to a bat containing an organic aromatic coloring agent of etching nature or an organic aromatic coloring agent, having insufl'icient etching action, in combination'with a material in rel.-

atively small amount that will provide the etching action on the metal. For instance, in the case of articles made from ma esium and its alloys, picric acidhas been ound to have the property of etching, coating, and coloring the same. The coating formed, which may vary in color from a pale yellow to-a black according to the treatment given,

moreover, otters a certain amount ofresistance to corrosion. The shade of the color,

where picric acid is used, is influenced by the strength of the solution (solubility 6.3 per cent in water at 100 C.) and its temperature as well as the length of time the article is treated or immersed in it, and the alloy used. Diphenyl sulphonic. acid (paraphenyl-benzene-sulphonic acid) likewise has the property of coating, coloring, and etching the magnesium article without the aid of additional .etchants. A magnesium-alumimum-manganese alloy article treated in a solution of this-material takes on a semi-white colorationiA coating applied on the metal by treatment with diphenyl sulphonic acid acts not only to change the surface appearmice of the article, but also gives some protection from'corrosion and is a paint base. On the other hand, naphthol yellow, Bismarck brown, aniline red, malachite green-hydrochloride, Congo red, quinoline yellow, acid fuchsine, alizarin blue, and the like, are preferabl used in a solution having an etchantv the other hand, ammonium chloride is a typical ammonium salt for use in the manner described, and sodium bisulphate is a suitable acid salt for use in etching the magnesium article. Where strong acids are used, we have found that a solution containing up to of 1 per cent of the acid is sufficient for most purposes, of 1 per cent being normally the preferred amount. Where weaker acids are used, they will'have to be used in higher concentrations to obtain an equivalent hydrogen ion concentration in the solution. .011 the other hand, where using ammonium salts, ammonium chloride is satisfactory and may beresent in the solution up to 5 per cent. he preferred amount found satisfactor for most purposes is of 1 per cent. hile we have given preferred amounts and specific ranges for these those exact amounts since, obviously, other amounts could be used in equivalent manner so long as the final effect is equivalent to that described. It is further to be noted that while we normally prefer to use an aqueous solution of the coloring and etching solution, at least part of the water can be replaced with other solvents such as alcohol. The

terminology etching solution as used herein is to be understood to cover not only a solution of a. material having both coloring and etching properties, but also a solution of a coloring material to which an etchant'pf the type described has been added.

' The use of the aromatic colorin materials noted above, which are. typi a 0f their classes, )ermits a large range of colors to be obtained on the articles being treated, such colors ranging from semi-white through yellow, brass, green, red, brown, and black. In

any case it will be understood that the particular color obtained will depend upon a number of variables, for instance, at higher temperatures the action is accelerated so that a shorter time will be required to obtain a given color for the same concentration of solution. The degree of concentration of the solution up to its saturation point also affects the coloring since with stronger solu tions the action is faster. The coloring material in the solvent may be present, if desired, in an amount in excess of its solubility therein, and will thus be available to go into solution as fast as the dissolved ma terial is used up in treating the'magnesium articles. The color will also vary with the dye used. Where an etching material is in the solution it also affects the lor tea certain extent. The particular y treated will likewise have some influence on the coloring. For instance, where an aqueous so lution containing of 1 per cent of quinoline yellow and of 1 per cent of ammonium chloride is used to treat a copper-containing magnesium alloy article, for instance, a mag materials, we do not wish to be limited to EXAMPLE 1 8G Brass colom'ngon a Do'wmcml F alloy 00nststing of magnesimn containing 4 per cent" aluminum and .25 per cent manganese I The article to be colored is first cleaned so as to be free from surface inclusions and contaminations and is then suspended in a bath which is composed as follows :3 per cent picric acid, 97 per cent wateiz, While the temperature of the bath may be substantially room temperature, we prefer to use a temperature of from'90 to 100 C., at which temperature 5 to seconds suflice .to bring out the brass coloring. The time, of course, may be varied from this to obtain the exact shade of color desired. During the treatment we prefer to frequently move the article or stir the bath so that any gas bubbles adhering to its surface will be. dislodged and thus permit a uniform coloring over the en-v tire surface of the article. At the, completion of the treatment the article is quickly removed from the solution and washed with water, preferably hot water which facilitates the quick drying of the article.

The following examples relate to the coloring offthe above noted Dowmetal alloy to obtain several other colors ExAMrL'E 2 Brownz'sh blew/l: coloring 3 per cent picric acid, 97 per cent water. The solution is preferably heated to a temperature of to C. and the article agitated therein for 10 to 15 minutes, following which it is quickly removed and washed.

EXAMPLE 3 yellowish green coiori'ng and washed. 1 7. v

EXAMPLE 4 Gray coloring of 1 per cent malachite greenhydrochloride, f of 1 per cent ammonium chlo-,

I ride, 99.8 per cent water. The cleaned Dowmetal'to-be coated is agitatedin thesolution at a temperature of 90 to 100 C. for 15 to minutes, following which it is quickly removed and washed.

EXAMPLE 5 Broelm coloring of 1- per cent naphthol yellow and of l per cent of sulphanilic acid, 99.4 per cent" water. The cleaned article is agitated for 5 1 minutes inthe solution at a temperature of 90 to 100 (1., following which it' is quickly removed and washed. 7

The socolored articles after being dried can be treated with a coat of lacquer or spirit varnish to further aid in preventing corrosion of the article or to retain the color obtained by the treatment as well as overcome discoloration due to abrasion. The article,

* thereto in the conventional manner.

onthe other hand, may have paint applied Such ,materials when applied to the surface of magnesium articles will be hereinafter rep ferred to as a protective coating.

' classes from which they are selected. These materials, moreover, are all organic aromatic compounds well known to those familiar with the dye art. Accordingly, since such materials, as a class, act as coloring agents on magnesium, they will be referred to generically in the claims as organic aromatic coloring agents for magnesium.

Other modes of applying the rinciple of our invention may employed instead of those explained, change being made as regards the process herem disclosed, provided the means stated by any of the following claims or the equivalent of such stated means be employed.

We therefore particularly point out and distinctly claim as our invention i 1. The method of treating a magnesium article which comprises subjecting said article to the actionqof an etching solution containing anorganic aromatic coloring agent for magnesium.

2. The method of'treating amagnesium article, which comprises subjecting same at a'temperature of 90 to 100 (lto the actionof an etching solution of an organic aromatic coloring agent for magnesium.

3. The method of treating a magnesium article, which comprises sulnecting same to the action of an etchin solution of one of the materials picric aci diphenyl sulphonic.

acid, naphthol yellow, Bismarck brown, ani-. line red, malachite green-hydrochloride, Congo red, alizarin blue.

quinoline yellow, acid fuchsine,

. 4. The method f treating a magnesium article, which comprises sub ecting same at a temperature of 90 to 100 C. to the action of an etching solution ofone of the materials picric acid, diphenyl sulphonic acid, naphthol yellow, Bismarck brown; aniline red, malachite green-hydrochloride, Congo red, quinoline yellow, acid fuchsine, alizarm'blue.

5. The method of coloring article, which comprises subjecting sameito the action ofanetching solution of an. organic aromatic coloring agent for'magnesium. Y

6. The method of coloring a. magnesium article, which comprisesthe steps-of cleana magnesium ing said article with an acid solution, and I treating it with an etching bath containing an organic aromatic coloring agent for nesium.

7. The method of'coloring a magnesium article, which comprises the steps of cleanlng said article with an acid solution, treating it with an etching bathcontaining an organic aromatic coloring agent for magnesium, and

- thereupon washing and drying the article.

8. The method of coloring ma esium and magnesium alloy articles, whic comprises subjecting same to the action of an etching solution of an acid type of organic aromatic coloringagent for magnesium.

9. The method of colorlng magnesium and ma nesium alloy articles which comprises subJecting same to the action of asolution of picric acid.

10. The method of coloring magnesium and magnesium alloy articles which conslsts in subjecting same to the action of an aqueous solution containing pieric acid in amount up. to its solubility therein.

11. The method of providing a magnesium or magnesium alloy article with a brass color, which consists in cleaning the article with an acid solution, thereupon agitating it in anaqueous solution of icric acid at a. temperature of to and as soon asthe required coloration has been obtained qulclfly rinsing it in water, and drying the art1- cle." 12. The method of coloring magnesium and inagnesiumalloy articles, which com-,

and :magnesiumalloy articles, which comprises subjecting same at a temperature of 90 to 100 C. to the action of an aqueous solution containing diphenyl sulphonic acid in amount up to its solubility therein.

14. The method of coloring magnesium and magnesium alloy articles, which coinprises subjecting same to the action of an etching solution of a basic type of organic aromatic coloring agent for magnesium.

15. The method of coloring magnesium and magnesium alloy articles, which com.- prises subjecting same to the action of an etching solution of malachite greenfhyclro chloride. W

15. The method of coloring magnesium and magnesium alloy articles, which core.-

prises subjecting same to the action of an etching aqueous solution containing malachite green-hydrochloride inamount up to its solubility therein.

17. The method of providing a magnesium or magnesium alloy article with a gray color, which consists in cleaning the article with an acid solution, thereupon agitating it in an aqueous solution of malachite greenhydrochloride and ammonium chloride at a temperature of'QQ" to 100 C. and as soon as the required coloration has been obtained quickly rinsing it in water, and drying the article.

18. A magnesium or magnesium alloy article provided with a closely adhering surface layer of a magnesium compound formed in place by the interaction of the magnesium with an etching solution of an organic aromatic coloring agent for magnesium.

19. A magnesium or magnesium alloy ticle provided with a closely adhering surface layer of a magnesiun compound formed in place by the interaction of the magnesium with an etching solution. of one of the materials pieric acid, diplienyl sui honic aciol, naphthol yellow, B mu bro'evn aniline red, malachite greenycirociiloririe, Congo red, quinoline yellow acid fuchsine, alizarin blue.

20. A magnesium or magnesium alloy article provided with a closely adhering surface layer of a magnesium compound formed in place by the interaction of the magnesium with picric acid.

21. A magnesium or'magnesium alloy article provided with a closely adhering surface layer ofa magnesium compound fcrmecl in placeby the interaction ofthe magnesium with diphenyl sulphomc acid.

'22. A magnesium or magnesium alloy article provided'with a closely adhering surface layer of a magnesium compound formed in place by the interaction of the magnesium with malachite greenhydrochloride.

Signed by us this 6th day of May 1931.

JOHN A. GA]? lVlLLlAlt l H. GRUDS. 

